There are known individually controllable refrigeration systems capable of meeting both a heating demand and a cooling demand in rooms at the same time. Such a refrigeration system includes a plurality of heat-using units placed in different rooms, respectively, so that some units perform cooling, and the other units perform heating.
Patent Document 1 discloses a refrigeration system of this kind. As shown in FIG. 12, a refrigeration system (100) includes a refrigerant circuit (101) in which a refrigerant circulates to perform a refrigeration cycle. The refrigerant circuit (101) includes a compressor (102), a heat-source heat exchanger (103), and first and second heat exchangers (first and second heat-using heat exchangers) (104, 105). A heat-source expansion valve (106) is provided near the heat-source heat exchanger (103), and first and second expansion valves (heat-using expansion valves) (107, 108) are provided near the heat-using heat exchangers (104, 105), respectively. The refrigerant circuit (101) further includes two three-way valves (109, 110), and first and second BS units (111, 112). Each of the BS units (111, 112) has two solenoid valves.
This refrigeration system (100) can perform a refrigeration cycle in which, for example, the heat-source heat exchanger (103) and the first heat-using heat exchanger (104) function as condensers, and the second heat-using heat exchanger (105) functions as an evaporator. In operation shown in FIG. 13, a refrigerant discharged from the compressor (102) is divided into two flows. One refrigerant flow condenses in the heat-source heat exchanger (103), passes through the full-open heat-source expansion valve (106), and flows into a liquid pipe (113). The other refrigerant flow passes through the first BS unit (111) and flows into the first heat-using heat exchanger (104). As a result, the refrigerant dissipates heat into indoor air in the first heat-using heat exchanger (104) to heat the room. After passing through the first heat-using expansion valve (107), the refrigerant flows into the liquid pipe (113), and joins with the refrigerant sent to the heat-source heat exchanger (103). The joined refrigerant is reduced in pressure as it passes through the second heat-using expansion valve (108), and then flows into the second heat-using heat exchanger (105). In the second heat-using heat exchanger (105), the refrigerant absorbs heat from the indoor air to cool the room. After that, the refrigerant passes through the second BS unit (112) and is sucked into the compressor (102).
In this manner, the refrigeration system (100) performs the refrigeration cycle by using the heat-using heat exchangers (104, 105) individually as the evaporator or the condenser, so as to allow independently switchable heating/cooling operation that satisfies both of the cooling and heating demands in the rooms at the same time.    Patent Document 1: Published Japanese Patent Application No. H11-241844